242 PROCEEDINGS OF SECTION C. 
Cornwall Mine the axinite veins contain all the metallic 
ingredients of the Colebrook, namely, pyrrhotite pyrite, 
arsenopyrite, and chalcopyrite; but here these mimerals 
have been deposited in a fissure, and are not due, at any rate 
where the vein is in the solid pyrites, to metasomatic re- 
placement. From these differences in the facts of the 
occurrences of the two classes of deposits, I draw the follow- 
ing’ conclusions : — 
1. Both classes of deposit were formed by emanations from 
one and the same granite magma. 
2. The pyritic tin deposits are probably products of 
emanations of slightly earlier birth than those which 
deposited the pyritic copper deposits of the Colebrook; the 
former having been deposited previous to, the latter con- 
temporaneous with, the axinite. 
3. If, however, it is proved at some future time, that in 
the case of the pyritic tin deposits, the latter are contem- 
poraneous with the formation of the axinite, which I think 
is still very possible, then I would suggest that the difference 
in the metallic contents of the pyritic tin deposits and tha 
pyritic copper deposits may be due to the fact that the latter 
are further removed from the seat of the granitic eruption. 
Barn Bluff Pyritic Deposits. 
The pyritic deposits in the vicinity of Barn Bluff, on the 
West Coast of Tasmania, lead us one step further in tracing 
the origin of pyritic deposits to plutonic agencies. The 
metallic contents of these deposits are essentially the same 
as those of the Colebrook Mine, namely, pyrrhotite, iron 
pyrites, markasite, copper pyrites, arsenical pyrites, with 
small quantities of gold and silver; to these, however, must 
be added specularite, which occurs disseminated through the 
other sulphides. Occasionally the ore consists of an intimate 
mixture of pyrrhotite, specularite, and fine fibres of actino- 
lite, when it has a very remarkable appearance, and when 
first found was mistaken by the prospectors for chalcocite. 
These deposits also are distinctly metasomatic, the solid 
pyrrhotite being often observed to pass over by imper- 
ceptible gradations into practically unmineralised quartzite. 
The ore-bodies consist of bands from 2 to 20 feet in thick- 
ness of ore and actinolite rock, with occasional bands of 
quartzite. The actinolite rock often contains a fair per- 
centage of copper pyrites through it. Like almost all pyritic 
deposits on the West Coast, these bands are conformable 
with the surrounding country, which strikes at this place 
a little north of west. At the Barn Bluff G.S. & C. Mine, 
which is the only one opened up to any extent as yet, the 
ore-body is bounded by a dyke of quartz-porphyry coursing 
